what is the mechanism of halogenation ?

Asked by yash joshi | 6th Oct, 2013, 10:06: PM

Expert Answer:

Halogenation involves the introduction of one or more halogen atoms (i.e. fluorine, chlorine, bromine or iodine) in the reactants. These reactants may be organic or inorganic species. The introduction of halogen atom(s) can be brought about by both substitution reaction as well as addition reaction. For example:

H2C=CH2 + Cl2 ? ClH2C-CH2Cl

 

take example of chlorination

1. Initiation: chlorin gives chlorin free radical by passing U.V. light

Cl-Cl gives Cl+Cl.

2. Propagation: chlorin free radical abstracts hydrogen from methane gives methyl free radical

Cl+CH4 gives  .CH3 +HCl

Methyl free radical gives methyl chloride and chlorine free radical

CH3 .  + Cl2 gives CH3Cl + Cl.

3. Termination: in this step all reactions are consumed and get terminated

Cl. +Cl. gives Cl2

CH3 + CH3 gives C2H6

CH3 . + Cl. gives CH3Cl

Remember: free radicals have dots (.) at superscript.

Answered by Hanisha Vyas | 7th Oct, 2013, 07:26: PM

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